Selective oxidation of CO in H2-rich stream over ZSM5 zeolites supported Ru catalysts: An investigation on the role of the support and the Ru particle size

Selective oxidation of CO in H2-rich stream over ZSM5 zeolites supported Ru catalysts: An investigation on the role of the support and the Ru particle size

Abstract

•Ru/ZSM5 catalysts exhibit higher CO2 yields compared to Ru/Al2O3, Ru/SiO2 and Ru/CeO2.•Ru supported on the ZSM5 with the highest SiO2/Al2O3 ratio is the most active system.•The form (−H or −Na) of the zeolite has a low effect on the catalytic perfomance.•The size of ruthenium particles increases with increasing the SiO2/Al2O3 ratio of the zeolite.•Bigger Ru particles enhance the PROX performance favoring CO and O2 activation on adjacent Ru sites.

Selective oxidation of CO in H2-rich stream was studied over ZSM5 zeolite supported Ru catalysts and the results were compared with those obtained over Ru samples supported on alumina, silica and ceria. ZSM5 zeolite supported Ru catalysts exhibited higher yields to CO2 than Ru samples on other supports. The SiO2/Al2O3 ratio of the zeolite was found to strongly affect the performance of the Ru/ZSM5 system, the Ru sample supported on the H-ZSM5 with the highest SiO2/Al2O3 ratio (280) being the most efficient towards the CO selective oxidation. The form of the zeolite (H- or Na-) had instead a lower influence. On the basis of characterization data (TEM, XPS, H2-TPR, NH3-TPD) it was pointed out that the performance of the Ru/ZSM5 samples are strongly dependent on the Lewis acidity of the zeolite and/or the Ru particle size, a lower number of Lewis acid sites and bigger Ru particles resulting in higher CO2 yields.